Vehicle head-lamp



"L W. BOUW-L vEHmLE HEAD LAMP; APPLICATION FILED AUG.26,19|6.

r S A M y uw fwww D P Mms wma man .wwf |L 1l|| -IL Hrs .A'T TDHNE'X UNITED STATES PATENT OFFICE.

THOMAS W. ROLPB'., 0F (ifLEVELAIN'D,v OHIO, ASSIGNOR, BY MESNE ASSIGNMENTS, TO CORNING GLASS WORKS, OF CORNING, NEW YORK, A CORPORATION OF NEW YORK.

VEHICLE HEAD-LAMP.

Specification of Letters lPatent.

Patented Feb. 1, 1921.

ticularly, the object is to eliminate all glare and at the saine time make use of all light rays issuing from the source for illuminating the points in the roadway which need the illumination most.

. An important feature of my invention resides in a novel redirecting `means for modifying the direction of the light rays after reflection, and in accordance therewith the degree of refraction depends upon the dis tance of the corresponding reflecting element from the `light source. This avoids certain difficulties usually encountered with light sources of distributed form, as the Yelectric incandescent filament lamp, which cannot be combined with reflectors in coinmon use to obtain uniform directional projection from all elements of the reflector. For instance, with a given light source located substantially at the focal point of a parabolic reflector, the reflected lightfrom each reflecting point is s read through a certain angle which depen s upon the angle subtended by the `lamp filament from that point on the reflector. This subtended angle in turn depends upon the distance of the reflecting element or point from the light source, the more remote the reflector the smaller the angle subtended, and vico versa. ln accordance with this principle, l design my correcting prisms with a progressively increasing refractive power as the corresponding reflecting elements approach the light source, and in the particular ap lication to non-glare headlamps the headlight plate has the correcting prisms horizontally arranged and progressively decreasing in angle or refractive power from the center outward.

-ln accordance with another feature of my invention l incorporate into the headlight plate a series of directing prisms for giving to the light the proper spread, and preferably these prisms are so designed and combined with the horizontally disposed prisms above set forth in such a manner that the roadsides are illuminated in an efficient and scientific manner from a point near the vehicle to the limit of the projection. To this' end these spreading prisms are vertically arranged and designed to have gradually decreasing refractory power from the center of thev plate in radial directions, the vvariation in. the refractive angle preferably corresponding to the progressive change in the refractorypower of the -abovey noted horizontally disposed prisms. With this arrangement the roadway surface is continuously illuminated from a point near the vehicle to the limit of light projection, and the roadsides are illuminated to practically the same depth at all points of the roadway, While the reflection of the rays above the horizontal plane is entirely avoided.

Inasmuch as the parabolic reflector is pretty generally used in vehicle headlamps,

have illustrated my invention as applied to this type of reflector, and my invention yparticularly contemplates a headlight plate embodying the above features and adapted to be used with the parabolic reflectors generally used in practice.

For a better 'understanding of my improved projector and headlight plate, reference may be had to the accompanying drawings, Figure 1 of which is a diagrammatic i lustration of the principle on which my invention is based; Fig. 2 is a front view of a headlight plate; Fig. 3 is a sectional view of the headlight plate on the line 3--3 4of Fig. 2; Fig. l is a front view of a headlight plate embodying another feature of my invention, and Fig. 5 is a sectional view of the headlight plate taken on the line 5--5 of Fig. 4;; Fig. 6 is a vertical sectional view illustrating a headlight plate having on one face the prisms shown in Figs. 2 and 3, and on the other face, the prisms shown in Figs. 4 and 5. v

Referring to Figs. l, 2 and 3, a parabolic reflector 1 and an incandescent lamp 2 of a common type used in projectors for vehicles are illustrated. The lamp 2 has a filament 3 which is located substantially at the focal point of the reflector 1. As is well limits of the light source 3, as indicated by full lines, these lines being drawn to certain points of the reflecting surface of' the reflector. As indicated, at each point on the reflector the reflected light is spread throu h '15 a certain angle which depends upon t e angle subtended bythe lamp filament from that point on the reflector, and this angle in turn depends upon the distance of that point on the reflector from the light source. It is apparent, therefore, that from a point at the back of the reflector which is relatively near'the light source the angle of reflected light is considerably larger than from a point near .the edge of the reflector which is farther or more remote from the light source. For example, with a lamp filament of certain dimensions located at the focus of an 8 parabola, the reflected light is spread 4&0 each side of the horizontal at .Nthe point of approximate maximum spread or inclination, while at the outer edge of the reflector where the spread is close to the minimum the angle of spread is only lf each side of the horizontal, the optical axis of the projector being horizontally disposed. It is important to avoid these rays above the horizontal, which, as known. cause glare to approaching drivers, and I avoid them by incorporating in the headlight plate 4 a series of horizontally disposed refracting prisms 5 which receive the reflected rays and bend them to or below the horizontal, but in designing and arranging these refracting elements I take into account the variation of the spread of the rays on the different points on the reflecting surface and make the prisms of different refractive powers or angles so that a prism has an angle which corresponds to the spiead of the rays on the corresponding reflecting element. The angle here referred to is that between the faces of the prisms 5 and the vertical, the refractive power of the prisms being readily determined by this angle, as is generally known. Specifically, I lay olf the surface of the plate into a number of zones, in the particular modification shown` four zones A to D, inclusive, and I make the prisms located in one zone of the same angle or refracting power; but these differ in angle from that of the prisms located in the other zones. For instance, the prisms 5 in zone A, which are located in the center of the plate, have a refracting power sufficient to bend the rays not less than 4% in the specific instance shown. so that none of the rays is nermitted to pass through this zone above the horizontal. In zone B, however, the prisms may be of a smaller angle inasmuch as the prisms in this zone correspond to elements on the reflecting surface which have i smaller spread than that in zone A, and in the specific instance shown the prisms in zone B have a refractory power or angle suilicient to bend the rays not less than 39j 75 oelow their normal direction. In like manner. Zones C and D have prisms of still smaller angles. the rays in each case being bent into parallelism with the horizontal or celow the horizontal. It is apparent, there- S0 fore. that these horizontal prisms are divided into longitudinal sections, the sections l:orresponding to the various zones through which they happen to pass and the refractng angle of the sections decreasing in both 85 directions with reference to a vertical line 3 3 through the plate. With this arrangement it is to be noted that the surface of the roadway is continuously illuminated from a point near the vehicle to the limit if the projection. The prisms in zone A light the surface of the roadway at a point near the vehicle. while the prisms in zone B illuminate the surface at a still farther distant point; and in like manner zones C ind D illuminate the surface at still farther iistant points. a practically uniform illuiniiation being obtained for the surface of the roadway from the nearest to the leniotcst points.

Theoretically the redirecting prisms should gradually change in angle from the -fenter of the plate to the outer edge. In order to simplify the design and manufacture. however, it may be suiiiciently accurate to divide the late into zones as indicated.

Figs. l andp 5 showa series of spreadinr prisms which may be used separate from and independent of the horizontal redirecting prisms, but are of special utility when com- '110 bined therewith for distributing the light in the most satisfactory manner for road illumination. In order to illuminate the roadway to the best advantage, it is desirable to spread the light to a greater angular distance to the side at a point near the automobile than at a considerable distance ahead thereof. For example a lateral spread of .50 might illuminate the roadway out to 20 feet on each side of the car at a point not far in front of the car. At a point a considerable distance. however, the same degree of lateral spread wbuld illuminate the roadway 4,0 or 50 feet on each side. This wide spread at a great distance in front of the car is undesirable as being unnecessary and results in a waste of light which could be better used in obtaining a higher intensity of illumination with a very slight lateral spread. Consequently, it is desirable to dill horizontal prisms.

s read laterally the light passing throu h t e plate in zone A a greater degree than t e light passing through the plate in zone B, and to spread the light in zone C less than in zone B, etc. The same idea of concentric division of prisms may, therefore, be applied to the spreading prisms on the plate, as above described in connection with the In accordance with this principle, the prisms 6 in zone A are designed to give wide spread of light, while the prisms in zone B give a medium spread of light; the prisms in zone C a slight spread, and the prisms in zone D preferably have noi spread of light at all, although it may be desirable to have the prisms in this outer zone give a slight spread. It is apparent, therefore, that the spreading prisms are divided into zones by concentric circles making the prisms in a zone of the same spreading angle and makingthe degree of spread of ,the prisms decrease in passing from the central zone to a zone at a greater distance from the center. j

In the specific embodiment shown, the

vertical prisms are illustrated as being on' the outside of the plate, and thehorizontal prisms on the inside thereof, but it is obvious that either of the groups of prisms may be located on the inside or on the exterior, according to choice. Preferably the two groups are on the opposite sides of the plate as is shown in Fig. 6, and it is obvious'also that either group may cover only `a part of the surface of the plate instead of the entire surface. Y v

What I claim and desire to secure by Let# ters Patent of the United States, is:

l. In a projector, the combination of a.

light source, a reiiector mounted in back thereof and a plate mounted in front of said light source provided with a series of transversely extending prisms receiving rays from the source after reflection by the re- Hector, the angles of the said prisms decreasing gradually in successive zones from the Center -of said plate to the periphery thereof substantially in all directions thus forming successive zones gradually decreasing in refractive power from the center ofthe plate.

2. In a projector, the combination of a li ht source and a reflector mounted in'r back o the same with a plate having a series of transversely extending refracting prisms disposed on both sides of a horizontal plane passing through said light source and symlnetrically disposed with reference to a point in said plane directly in front of the center of said light source, the refractive angle and the refractive power of said prisms decreasing progressively as the distance from the said point increases in substantially all directions in the plane of said prisms.

3. In a projector, the combination of a light source and a parabolic reflector mounted in back of said light source of a circular headlight plate mounted in front of said vof said prisms increasing progressively from the center along any radius to the circumference of said headlight plate.

4. In a projector, the combination of a light source and a parabolic reflector mount.- ed in back of the same with a substantially circular headlight plate mounted in front thereof having a series of horizontal prisms thereon, said prisms being divided into sec'- tions of different refractive powers and angles and said refractive powers and an les decreasing from the center along any ra ius to the circumference of said headlight plate.

In a projector, the combination of a parabolic reiiector and an electric incandescent lament lamp located substantially at the focal point, with a headlight plate comprisin a series of horizontal refracting prisms, said prisms bein divided by concen- ,tr1c circles into zones o prisms of different refractive angles progressively decreasing from the center outward.

6. In a projector, the combination of a parabolic reflector and an electric incandescent filament lamp located substantially atI the focal point, with a headlight plate embodying a series of horizontal refracting ribs progressively decreasing in angle from the center of the plate in radial directions, and other ribs vertically disposed for spreading the light after reflection and also having angles progressively decreasing from the center of the plate in radial directions.

7. .In a projector, the combination of a parabolic reflector and an electric incandescent filament lamp located substantially at the focal point, with a headlight plate embodying in one surface a series of refracting ribs horizontally disposed for bending the light downwardly, and on the other surface a series of vertically disposed spreading ribs, said ribs being divided by concentric circles into zones of progressively decreasing refractive' powers from the center outwar in radial directions.

8. A headlight plate embodying a series of refracting ribs, said ribs bein divided by concentric circles into z ones o rogressively decreasing refractive powers rom the center outward in radial directions and above and below said center.

9. A headli ht plate embodying a series of substantialfy vertical spreading prisms divided by concentric circles into zones of progressively decreasing refractive powers from the center of the plate outward in radial directions and above and below said center.

10. A headlight plate embodying on one surface a Series of refracting ribs divided by concentric circles into zones of progressively decreasing refractive powers from the center of the plate outward in radial directions, and on the other surface a series of spreading ribs.

11. A headlight plate embodying on one surface a series of refracting ribs and on the other surface a series of spreading ribs at right angles to the aforesaid prisms, said plate being divided by concentric circles into zones of ribs of progressively decreasing angles from the center of the plate outward in radial directions.

12. A headlight plate provided with a series of substantially horizontally extending refracting ribs and a series of substantially vertically extending light spreading ribs, said horizontally extending ribs being divided into concentric zones and the ribs of the zones farther from the center being of less refractive power than those closer to the center.

13. A headlight plate provided with a series of substantially vertical ribs arranged on both sides of the center of said plate said ribs being of decreasing refractive angle or power as the periphery of said plate is approached.

14. A cover glass having thereon a series of horizontal prisms, the vertical refractive power of each prism being less at its ends than at its center.

15. A cover glass having thereon a series i of horizontal prisms of varying refractive power, the vertical refractive power of each prism being less at its ends than at its center.

16. A headlight cover, the vertical refractive power of which is greater at several points in its medial vertical plane than at -ooints away from such medial plane but in the same horizontal planes.

i7. A headlight cover in which the verti- :ai refractive power varies at points in the same horizontal plane, decreasing from the center outwardly.

18. In a lighting system, the combination with a light source. of a mirror reflecting the rays thereof. and a refracting cover glass, the vertical refractive power of such glass being greater adjacent to the center of a horizontal plane therethrough than at points in such plane farther away from the center.

L9. The combination with a reflector and a light source located at approximately the focal point thereof. of a cover plate for the reflector having refracting elements thereon so located as to receive light from the source after reflection by the reflector, the refractive power of the elements on both sides of :he center along at least one diameter of the plate generally varying inversely from a maximum at the center inversely with their distance from the center.

Z0. A refracting cover plate for a refiecting projector. the refraction produced by a plurality of parts thereof located on both sides of the center along at least one diameter of the plate being in the same general direction. and varying in extent from a maximum at the center inversely with the distance of each of such parts from the center.

n witness whereof. I have hereunto set mv hand this 24th dav of August. 1916.

"THOMAS W. ROLPH. 

